Add Captions to a Video, Free — No Upload
Auto-transcribe and burn subtitles into a video with Whisper — in your browser, nothing uploaded.
Select an audio or video file
MP3, WAV, M4A, MP4, MOV, WebM — transcribed in your browser with Whisper
Click to choose, or drop a file here
About burning captions into a video in the browser
This transcribes a video's speech with the same in-browser Whisper model as Video to Text, then lets you fix any mistakes before either exporting SRT/VTT subtitle files or burning the caption text directly into the video as a new file — visible whether or not the platform it ends up on supports subtitle tracks. Both the transcription and the burn-in step run entirely on your device through WebAssembly and WebCodecs; nothing is uploaded.
Burning in is a full re-encode: each frame is decoded, the active caption line is drawn onto it with a bold white-on-black-stroke style at the position and size you choose, and the frame is re-encoded back into the same container the video came in as (MP4 stays MP4, WebM stays WebM). Because the text becomes part of the picture, review and correct every line first — that's the whole reason the caption list is editable before the burn-in step, not after.
Supported files
Accepts MP4, MOV, WebM and other video your browser can play (it needs an audio track). Exports .txt, .srt and .vtt.
Is my file uploaded?
No. Whisper runs entirely in your browser via WebAssembly — the video and its audio never leave your device.
Common problems
- "Couldn't read audio from this file"
- The video may have no audio track, or your browser can't decode its audio codec. Extract the audio first (Video to MP3) and transcribe that.
- It's very slow
- WASM transcription runs at roughly 1–5× real time. Switch to the Tiny model, or trim the video to the part you need first.
- The text has errors
- Whisper isn't perfect — proofread. Setting the exact language instead of Auto-detect, and using the Base model, both help.
How to Add Captions to Video
- 1
Add your video
Drop in an MP4, MOV or WebM with an audio track — it's read in your browser, never uploaded.
- 2
Transcribe and review
Whisper transcribes the speech into timed caption lines. Fix any mistakes right in the list before you burn them in — corrections after that point mean starting over.
- 3
Style and export
Pick a position and size, then download SRT/VTT subtitle files, or burn the captions directly into the video as a new file.
Related PDF tools
Add Captions to Video — frequently asked questions
Is my video uploaded?+
No. Both the Whisper transcription and the caption burn-in run entirely in your browser. The video never leaves your device.
Which browsers work?+
Transcription works broadly. Burning captions into the video needs WebCodecs — Chrome, Edge or Safari 17+. You can still download SRT/VTT subtitle files anywhere transcription works.
Can I fix mistakes before burning them in?+
Yes — every caption line is editable after transcription. Fix anything Whisper got wrong before you burn it in, since that step is permanent.
Does burning in captions reduce video quality?+
Slightly — it's a full re-encode of the video, the same trade-off as Compress Video. Pick a lower resolution source if file size matters more than quality.
Do you upload my files to a server?+
No — every tool here processes your files entirely on your device, and nothing is uploaded to a server. The only exception is the AI tools, which send the extracted text (not the file) to Claude to do their work.
Is there a file size limit?+
There's no artificial limit we impose, but since processing happens in your browser, very large files (500+ MB or 1,000+ pages) are limited by your device's memory rather than by us.
Advertisement
Advertisement